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Article

Biphasic Packing of DNA and Internal Proteins in Bacteriophage T4 Heads Revealed by Bubblegram Imaging

1
Laboratory of Structural Biology Research, National Institute of Arthritis Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892-8025, USA
2
Department of Biochemistry and Molecular Biology, University of Maryland Medical School, Baltimore, MD 21201-1503, USA
3
Physics Department, Technische Universität München, 85748 Garching-bei-München, Germany
*
Author to whom correspondence should be addressed.
These authors contributed equally.
Present address: CMM Group, Leidos Medical Research, Frederick, MD 21701, USA.
§
Deceased.
Viruses 2020, 12(11), 1282; https://doi.org/10.3390/v12111282
Received: 11 September 2020 / Revised: 3 November 2020 / Accepted: 4 November 2020 / Published: 10 November 2020
(This article belongs to the Special Issue In Memory of Michael Rossmann)
The virions of tailed bacteriophages and the evolutionarily related herpesviruses contain, in addition to highly condensed DNA, substantial quantities of internal proteins. These proteins (“ejection proteins”) have roles in scaffolding, maturational proteolysis, and cell-to-cell delivery. Whereas capsids are amenable to analysis at high resolution by cryo-electron microscopy, internal proteins have proved difficult to localize. In this study, we investigated the distribution of internal proteins in T4 by bubblegram imaging. Prior work has shown that at suitably high electron doses, radiation damage generates bubbles of hydrogen gas in nucleoprotein specimens. Using DNA origami as a test specimen, we show that DNA does not bubble under these conditions; it follows that bubbles represent markers for proteins. The interior of the prolate T4 head, ~1000 Å long by ~750 Å wide, has a bubble-free zone that is ~100–110 Å thick, underlying the capsid shell from which proteins are excluded by highly ordered DNA. Inside this zone, which is plausibly occupied by ~4 layers of coaxial spool, bubbles are generated at random locations in a disordered ensemble of internal proteins and the remainder of the genome. View Full-Text
Keywords: cryo-electron microscopy; DNA packaging; coaxial spool; DNA origami; radiation damage; bubblegram cryo-electron microscopy; DNA packaging; coaxial spool; DNA origami; radiation damage; bubblegram
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MDPI and ACS Style

Wu, W.; Cheng, N.; Black, L.W.; Dietz, H.; Steven, A.C. Biphasic Packing of DNA and Internal Proteins in Bacteriophage T4 Heads Revealed by Bubblegram Imaging. Viruses 2020, 12, 1282. https://doi.org/10.3390/v12111282

AMA Style

Wu W, Cheng N, Black LW, Dietz H, Steven AC. Biphasic Packing of DNA and Internal Proteins in Bacteriophage T4 Heads Revealed by Bubblegram Imaging. Viruses. 2020; 12(11):1282. https://doi.org/10.3390/v12111282

Chicago/Turabian Style

Wu, Weimin, Naiqian Cheng, Lindsay W. Black, Hendrik Dietz, and Alasdair C. Steven 2020. "Biphasic Packing of DNA and Internal Proteins in Bacteriophage T4 Heads Revealed by Bubblegram Imaging" Viruses 12, no. 11: 1282. https://doi.org/10.3390/v12111282

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